I have a bitbucket account and opened a git repo there. I worked with the command line and made a few simple test commits for a few simple text files. It's actually quite simple, if I just do the, um, standard things with it, for the lack of a better term. So far, so good.

Now I would like to use a git client with a GUI on the said repo. I intend to do this on Xubuntu 13.10 first, afterwards on Windows 7 as well.

Say I use git gui or git-cola, do I simply open the folder on my PC and that's it?

First thing is bit bucket use git same as github or any other git repo. So there is no difference in a bit bucket repo and other git repo. For GUI u can try gitk which looks ugly but work nicely. There are other GUI apps also like gitg, webgit and other. U can use any of them. But remember u can more productive if u use command line (my personal thought.)